Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Commitments to Extend Credit
Letters of credit	$ 3,000	$ 3,000
Allowance for unfunded credit commitments	47	49
Standby Letters of Credit
Commitments to Extend Credit
Letters of credit	3,000	2,900
Commercial Letters of Credit
Commitments to Extend Credit
Letters of credit	$ 39	$ 31